Mysterious life forms identified in the extreme deep sea

Oceanographers document the deepest-known existence of giant amoebas in the Mariana Trench.

Scientists at Scripps Institution of Oceanography at UC San Diego have identified gigantic amoebas at one of the deepest locations on Earth — the Pacific Ocean’s Mariana Trench.

During a July 2011 voyage, the researchers and National Geographic engineers deployed untethered free-falling/ascending landers equipped with digital video and lights to search the largely unexplored region and documented the deepest-known existence of xenophyophores, single-celled animals found exclusively in deep-sea environments.

Xenophyophores are noteworthy for their size — with individual cells often exceeding four inches (10 centimeters) — and also for their extreme abundance on the seafloor and their role as hosts for a variety of organisms.

The researchers spotted the life forms at depths up to 6.6 miles (10,641 meters) within the Sirena Deep of the Mariana Trench. The previous depth record for xenophyophores was approximately 4.7 miles (7,500 meters) in the New Hebrides Trench, although sightings in the deepest portion of the Mariana Trench have been reported.

Scientists say xenophyophores are the largest individual cells in existence. Recent studies indicate that by trapping particles from the water, xenophyophores can concentrate high levels of lead, uranium and mercury and are thus likely resistant to large doses of heavy metals. They also are well-suited to a life of darkness, low temperature and high pressure in the deep sea.

The Mariana Trench is the deepest part of the world’s oceans, reaching a maximum-known depth of about 6.78 miles (10.91 kilometres) at the Challenger Deep, a small slot-shaped valley in its floor. Via Wikipedia

According to the researchers, the xenophyophores are just the tip of the iceberg when it comes to diversity of life at extreme depths.

National Geographic engineers created a Dropcam underwater camera to allow scientists and filmmakers to capture high-quality footage from any depth in the ocean. The device has a thick-walled glass sphere capable of withstanding more than eight-tons-per-square-inch pressure at extreme depth. Seafloor animals are lured to the camera with bait.

Deep-sea biologist Lisa Levin of the Scripps Institution said:

Xenophyophores … are fascinating giants that are highly adapted to extreme conditions but at the same time are very fragile and poorly studied. These and many other structurally important organisms in the deep sea need our stewardship as human activities move to deeper waters.

Bottom line: Lisa Levin, Scripps Institution of Oceanography at UC San Diego, and her team have identified gigantic amoebas at a depth of 6.6 miles in the Pacific Ocean’s Mariana Trench. The team used a Dropcam created by National Geographic engineers for the July 2011 voyage.